feat(core): B4 price oscillators (TsfOscillator, MacdHistogram, PpoHistogram) (#184)

Adds three **Price Oscillators** family indicators (420 → 423).

## Indicators

- **TsfOscillator** — `100·(close − TSF)/close`, the percentage gap of the close to the **one-bar-ahead** time-series forecast. Close-relative companion to `Cfo`, which measures the same gap against the regression value at the *current* bar; the two differ by exactly the slope term `100·b/close`.
- **MacdHistogram** — the standalone `macd − signal` bar of MACD exposed as a plain `f64` series.
- **PpoHistogram** — the Percentage Price Oscillator with its 9-period signal EMA and the resulting scale-free, zero-centered histogram (PPO itself only emits the line).

All three are scalar `f64` indicators wrapping existing, already-tested building blocks (`MacdIndicator`, `Ppo` + `Ema`, `Tsf`).

## Scope notes (VORAB-CHECK)

The B4 roadmap listed six items; three were dropped to avoid duplicates:
- *Forecast Oscillator* already ships as `Cfo`.
- *Derivative Oscillator* already ships (`DerivativeOscillator`, B2).
- *Detrended Synthetic Price* deferred — no citable formula distinct from the existing `Apo`/`Dpo`.

## Touchpoints

Core (`tsf_oscillator.rs`, `macd_histogram.rs`, `ppo_histogram.rs`) with full per-branch unit tests, `mod.rs`/`lib.rs`, python/node/wasm bindings (wasm via typed-arg macro, python/node hand-written for the multi-arg histograms), fuzz drivers, python reference + streaming-vs-batch tests, node factories, README family row + counter, CHANGELOG.

Local verify: `cargo test --workspace` green, `clippy -D warnings` clean, node 498 tests, full python suite green.

crates/wickra-core/src/indicators/macd_histogram.rs

@@ -0,0 +1,184 @@
+//! MACD Histogram (standalone).
+
+use crate::error::Result;
+use crate::indicators::macd::MacdIndicator;
+use crate::traits::Indicator;
+
+/// MACD Histogram — the `macd − signal` bar of [`MacdIndicator`] as a
+/// standalone scalar indicator.
+///
+/// ```text
+/// macd      = EMA(fast) − EMA(slow)
+/// signal    = EMA(macd, signal)
+/// histogram = macd − signal
+/// ```
+///
+/// The histogram is the most actively traded part of MACD: it crosses zero
+/// exactly when the MACD line crosses its signal, and its slope measures
+/// whether that momentum is accelerating or fading. This wrapper exposes just
+/// that series for pipelines that want a plain `f64` stream rather than the
+/// full [`MacdOutput`](crate::MacdOutput); for the line and signal alongside
+/// it, use [`MacdIndicator`](crate::MacdIndicator) directly.
+///
+/// Standard parameters are `fast = 12`, `slow = 26`, `signal = 9`, so the
+/// first value lands after `slow + signal − 1` inputs — exactly when
+/// [`MacdIndicator`] emits its first full output.
+///
+/// # Example
+///
+/// ```
+/// use wickra_core::{Indicator, MacdHistogram};
+///
+/// let mut indicator = MacdHistogram::new(12, 26, 9).unwrap();
+/// let mut last = None;
+/// for i in 0..80 {
+///     last = indicator.update(100.0 + f64::from(i));
+/// }
+/// assert!(last.is_some());
+/// ```
+#[derive(Debug, Clone)]
+pub struct MacdHistogram {
+    macd: MacdIndicator,
+}
+
+impl MacdHistogram {
+    /// Construct a MACD histogram with the given periods.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`Error::PeriodZero`] if any period is zero, and
+    /// [`Error::InvalidPeriod`] if `fast >= slow`.
+    pub fn new(fast: usize, slow: usize, signal: usize) -> Result<Self> {
+        Ok(Self {
+            macd: MacdIndicator::new(fast, slow, signal)?,
+        })
+    }
+
+    /// Default `(12, 26, 9)` configuration, matching every classical chart package.
+    pub fn classic() -> Self {
+        Self::new(12, 26, 9).expect("classic MACD periods are valid")
+    }
+
+    /// Configured periods as `(fast, slow, signal)`.
+    pub const fn periods(&self) -> (usize, usize, usize) {
+        self.macd.periods()
+    }
+}
+
+impl Indicator for MacdHistogram {
+    type Input = f64;
+    type Output = f64;
+
+    fn update(&mut self, input: f64) -> Option<f64> {
+        self.macd.update(input).map(|out| out.histogram)
+    }
+
+    fn reset(&mut self) {
+        self.macd.reset();
+    }
+
+    fn warmup_period(&self) -> usize {
+        self.macd.warmup_period()
+    }
+
+    fn is_ready(&self) -> bool {
+        self.macd.is_ready()
+    }
+
+    fn name(&self) -> &'static str {
+        "MacdHistogram"
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::error::Error;
+    use crate::traits::BatchExt;
+    use approx::assert_relative_eq;
+
+    #[test]
+    fn rejects_invalid_periods() {
+        assert!(matches!(
+            MacdHistogram::new(0, 26, 9),
+            Err(Error::PeriodZero)
+        ));
+        assert!(matches!(
+            MacdHistogram::new(12, 26, 0),
+            Err(Error::PeriodZero)
+        ));
+        assert!(matches!(
+            MacdHistogram::new(26, 12, 9),
+            Err(Error::InvalidPeriod { .. })
+        ));
+    }
+
+    #[test]
+    fn accessors_and_metadata() {
+        let osc = MacdHistogram::classic();
+        assert_eq!(osc.periods(), (12, 26, 9));
+        assert_eq!(osc.name(), "MacdHistogram");
+        assert_eq!(osc.warmup_period(), 26 + 9 - 1);
+        assert!(!osc.is_ready());
+    }
+
+    #[test]
+    fn equals_macd_histogram_field() {
+        // The standalone series must be exactly MacdIndicator's histogram bar.
+        let prices: Vec<f64> = (1..=120)
+            .map(|i| 100.0 + (f64::from(i) * 0.25).sin() * 8.0)
+            .collect();
+        let hist = MacdHistogram::classic().batch(&prices);
+        let full = MacdIndicator::classic().batch(&prices);
+        assert_eq!(hist.len(), full.len());
+        for (h, m) in hist.iter().zip(full.iter()) {
+            assert_eq!(h.is_some(), m.is_some());
+            if let (Some(h), Some(m)) = (h, m) {
+                assert_relative_eq!(*h, m.histogram, epsilon = 1e-12);
+            }
+        }
+    }
+
+    #[test]
+    fn warmup_emits_first_value_at_warmup_period() {
+        let mut osc = MacdHistogram::new(3, 6, 3).unwrap();
+        let warmup = osc.warmup_period();
+        assert_eq!(warmup, 6 + 3 - 1);
+        for i in 1..warmup {
+            assert!(osc.update(100.0 + i as f64).is_none());
+        }
+        assert!(osc.update(100.0 + warmup as f64).is_some());
+        assert!(osc.is_ready());
+    }
+
+    #[test]
+    fn constant_series_converges_to_zero() {
+        let mut osc = MacdHistogram::classic();
+        let out = osc.batch(&[100.0_f64; 200]);
+        let last = out.iter().rev().flatten().next().expect("emits a value");
+        assert_relative_eq!(*last, 0.0, epsilon = 1e-9);
+    }
+
+    #[test]
+    fn batch_equals_streaming() {
+        let prices: Vec<f64> = (1..=100)
+            .map(|i| (f64::from(i) * 0.4).cos() * 10.0)
+            .collect();
+        let mut a = MacdHistogram::classic();
+        let mut b = MacdHistogram::classic();
+        assert_eq!(
+            a.batch(&prices),
+            prices.iter().map(|p| b.update(*p)).collect::<Vec<_>>()
+        );
+    }
+
+    #[test]
+    fn reset_clears_state() {
+        let mut osc = MacdHistogram::classic();
+        osc.batch(&(1..=80).map(f64::from).collect::<Vec<_>>());
+        assert!(osc.is_ready());
+        osc.reset();
+        assert!(!osc.is_ready());
+        assert_eq!(osc.update(1.0), None);
+    }
+}

crates/wickra-core/src/indicators/mod.rs

@@ -214,6 +214,7 @@ mod ma_envelope;
 mod macd;
 mod macd_ext;
 mod macd_fix;
+mod macd_histogram;
 mod mama;
 mod market_facilitation_index;
 mod marubozu;
@@ -270,6 +271,7 @@ mod pmo;
 mod point_and_figure_bars;
 mod polarized_fractal_efficiency;
 mod ppo;
+mod ppo_histogram;
 mod profit_factor;
 mod psar;
 mod pvi;
@@ -381,6 +383,7 @@ mod triple_top_bottom;
 mod trix;
 mod true_range;
 mod tsf;
+mod tsf_oscillator;
 mod tsi;
 mod tsv;
 mod ttm_squeeze;
@@ -634,6 +637,7 @@ pub use ma_envelope::{MaEnvelope, MaEnvelopeOutput};
 pub use macd::{MacdIndicator, MacdOutput};
 pub use macd_ext::{MaType, MacdExt};
 pub use macd_fix::MacdFix;
+pub use macd_histogram::MacdHistogram;
 pub use mama::{Mama, MamaOutput};
 pub use market_facilitation_index::MarketFacilitationIndex;
 pub use marubozu::Marubozu;
@@ -690,6 +694,7 @@ pub use pmo::Pmo;
 pub use point_and_figure_bars::{PnfColumn, PointAndFigureBars};
 pub use polarized_fractal_efficiency::PolarizedFractalEfficiency;
 pub use ppo::Ppo;
+pub use ppo_histogram::PpoHistogram;
 pub use profit_factor::ProfitFactor;
 pub use psar::Psar;
 pub use pvi::Pvi;
@@ -801,6 +806,7 @@ pub use triple_top_bottom::TripleTopBottom;
 pub use trix::Trix;
 pub use true_range::TrueRange;
 pub use tsf::Tsf;
+pub use tsf_oscillator::TsfOscillator;
 pub use tsi::Tsi;
 pub use tsv::Tsv;
 pub use ttm_squeeze::{TtmSqueeze, TtmSqueezeOutput};
@@ -973,6 +979,9 @@ pub const FAMILIES: &[(&str, &[&str])] = &[
             "ZeroLagMacd",
             "ElderImpulse",
             "Stc",
+            "TsfOscillator",
+            "MacdHistogram",
+            "PpoHistogram",
         ],
     ),
     (
@@ -1414,6 +1423,6 @@ mod family_tests {
         // the actual indicator count is the early-warning signal that an
         // indicator was added without being assigned a family.
         let total: usize = FAMILIES.iter().map(|(_, ns)| ns.len()).sum();
-        assert_eq!(total, 420, "FAMILIES total drifted from indicator count");
+        assert_eq!(total, 423, "FAMILIES total drifted from indicator count");
     }
 }

crates/wickra-core/src/indicators/ppo_histogram.rs

@@ -0,0 +1,230 @@
+//! Percentage Price Oscillator Histogram.
+
+use crate::error::{Error, Result};
+use crate::indicators::ema::Ema;
+use crate::indicators::ppo::Ppo;
+use crate::traits::Indicator;
+
+/// PPO Histogram — the `ppo − signal` bar of the Percentage Price Oscillator.
+///
+/// ```text
+/// ppo       = 100 · (EMA_fast − EMA_slow) / EMA_slow
+/// signal    = EMA(ppo, signal_period)
+/// histogram = ppo − signal
+/// ```
+///
+/// [`Ppo`](crate::Ppo) itself only emits the percentage line; this indicator
+/// adds the classic 9-period signal EMA on top and reports the resulting
+/// zero-centered histogram. Because PPO is scale-free (the EMA gap is divided
+/// by the slow EMA), the histogram is **comparable across instruments** — a
+/// PPO histogram of `0.4` means the same relative momentum on any asset, unlike
+/// the price-unit [`MacdHistogram`](crate::MacdHistogram).
+///
+/// With Appel's defaults `fast = 12`, `slow = 26`, `signal = 9`, the first
+/// value lands after `slow + signal − 1` inputs — the point at which the slow
+/// EMA and then the signal EMA are both seeded.
+///
+/// # Example
+///
+/// ```
+/// use wickra_core::{Indicator, PpoHistogram};
+///
+/// let mut indicator = PpoHistogram::new(12, 26, 9).unwrap();
+/// let mut last = None;
+/// for i in 0..80 {
+///     last = indicator.update(100.0 + f64::from(i));
+/// }
+/// assert!(last.is_some());
+/// ```
+#[derive(Debug, Clone)]
+pub struct PpoHistogram {
+    ppo: Ppo,
+    signal_ema: Ema,
+    signal_period: usize,
+    current: Option<f64>,
+}
+
+impl PpoHistogram {
+    /// Construct a PPO histogram with the `fast`/`slow` EMA periods and the
+    /// `signal` EMA period.
+    ///
+    /// # Errors
+    ///
+    /// Returns [`Error::PeriodZero`] if any period is `0`, or
+    /// [`Error::InvalidPeriod`] if `fast >= slow`.
+    pub fn new(fast: usize, slow: usize, signal: usize) -> Result<Self> {
+        if signal == 0 {
+            return Err(Error::PeriodZero);
+        }
+        Ok(Self {
+            ppo: Ppo::new(fast, slow)?,
+            signal_ema: Ema::new(signal)?,
+            signal_period: signal,
+            current: None,
+        })
+    }
+
+    /// Default `(12, 26, 9)` configuration.
+    pub fn classic() -> Self {
+        Self::new(12, 26, 9).expect("classic PPO periods are valid")
+    }
+
+    /// Configured periods as `(fast, slow, signal)`.
+    pub const fn periods(&self) -> (usize, usize, usize) {
+        let (fast, slow) = self.ppo.periods();
+        (fast, slow, self.signal_period)
+    }
+
+    /// Current value if available.
+    pub const fn value(&self) -> Option<f64> {
+        self.current
+    }
+}
+
+impl Indicator for PpoHistogram {
+    type Input = f64;
+    type Output = f64;
+
+    fn update(&mut self, input: f64) -> Option<f64> {
+        // Guard before touching either stage so a non-finite input never
+        // advances the signal EMA on a stale, re-fed PPO value.
+        if !input.is_finite() {
+            return self.current;
+        }
+        let ppo = self.ppo.update(input)?;
+        let signal = self.signal_ema.update(ppo)?;
+        let histogram = ppo - signal;
+        self.current = Some(histogram);
+        Some(histogram)
+    }
+
+    fn reset(&mut self) {
+        self.ppo.reset();
+        self.signal_ema.reset();
+        self.current = None;
+    }
+
+    fn warmup_period(&self) -> usize {
+        // Slow EMA seeds the PPO, then the signal EMA needs `signal − 1` more.
+        self.ppo.warmup_period() + self.signal_period - 1
+    }
+
+    fn is_ready(&self) -> bool {
+        self.current.is_some()
+    }
+
+    fn name(&self) -> &'static str {
+        "PpoHistogram"
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::traits::BatchExt;
+    use approx::assert_relative_eq;
+
+    #[test]
+    fn rejects_invalid_periods() {
+        assert!(matches!(
+            PpoHistogram::new(0, 26, 9),
+            Err(Error::PeriodZero)
+        ));
+        assert!(matches!(
+            PpoHistogram::new(12, 0, 9),
+            Err(Error::PeriodZero)
+        ));
+        assert!(matches!(
+            PpoHistogram::new(12, 26, 0),
+            Err(Error::PeriodZero)
+        ));
+        assert!(matches!(
+            PpoHistogram::new(26, 12, 9),
+            Err(Error::InvalidPeriod { .. })
+        ));
+    }
+
+    #[test]
+    fn accessors_and_metadata() {
+        let osc = PpoHistogram::classic();
+        assert_eq!(osc.periods(), (12, 26, 9));
+        assert_eq!(osc.name(), "PpoHistogram");
+        assert_eq!(osc.warmup_period(), 26 + 9 - 1);
+        assert_eq!(osc.value(), None);
+        assert!(!osc.is_ready());
+    }
+
+    #[test]
+    fn equals_ppo_minus_signal_ema() {
+        // The histogram must equal PPO minus an EMA(signal) composed by hand.
+        let prices: Vec<f64> = (1..=120)
+            .map(|i| 100.0 + (f64::from(i) * 0.2).sin() * 6.0)
+            .collect();
+        let got = PpoHistogram::new(12, 26, 9).unwrap().batch(&prices);
+
+        let mut ppo = Ppo::new(12, 26).unwrap();
+        let mut sig = Ema::new(9).unwrap();
+        let mut expected = Vec::with_capacity(prices.len());
+        for p in &prices {
+            let out = ppo
+                .update(*p)
+                .and_then(|line| sig.update(line).map(|signal| line - signal));
+            expected.push(out);
+        }
+        assert_eq!(got, expected);
+    }
+
+    #[test]
+    fn warmup_emits_first_value_at_warmup_period() {
+        let mut osc = PpoHistogram::new(3, 6, 3).unwrap();
+        let warmup = osc.warmup_period();
+        assert_eq!(warmup, 6 + 3 - 1);
+        for i in 1..warmup {
+            assert!(osc.update(100.0 + i as f64).is_none());
+        }
+        assert!(osc.update(100.0 + warmup as f64).is_some());
+        assert!(osc.is_ready());
+    }
+
+    #[test]
+    fn constant_series_converges_to_zero() {
+        let mut osc = PpoHistogram::classic();
+        let out = osc.batch(&[100.0_f64; 200]);
+        let last = out.iter().rev().flatten().next().expect("emits a value");
+        assert_relative_eq!(*last, 0.0, epsilon = 1e-9);
+    }
+
+    #[test]
+    fn ignores_non_finite_input() {
+        let mut osc = PpoHistogram::new(3, 6, 3).unwrap();
+        let out = osc.batch(&(1..=40).map(f64::from).collect::<Vec<_>>());
+        let before = *out.last().unwrap();
+        assert!(before.is_some());
+        assert_eq!(osc.update(f64::NAN), before);
+        assert_eq!(osc.update(f64::INFINITY), before);
+        assert_eq!(osc.value(), before);
+    }
+
+    #[test]
+    fn batch_equals_streaming() {
+        let prices: Vec<f64> = (1..=100)
+            .map(|i| 100.0 + (f64::from(i) * 0.4).cos() * 10.0)
+            .collect();
+        let mut a = PpoHistogram::classic();
+        let mut b = PpoHistogram::classic();
+        assert_eq!(
+            a.batch(&prices),
+            prices.iter().map(|p| b.update(*p)).collect::<Vec<_>>()
+        );
+    }
+
+    #[test]
+    fn reset_clears_state() {
+        let mut osc = PpoHistogram::classic();
+        osc.batch(&(1..=80).map(f64::from).collect::<Vec<_>>());
+        assert!(osc.is_ready());
+        osc.reset();
+        assert!(!osc.is_ready());
+        assert_eq!(osc.update(1.0), None);
+    }
+}

crates/wickra-core/src/indicators/tsf_oscillator.rs

@@ -0,0 +1,206 @@
+//! Time Series Forecast Oscillator (TSF Oscillator).
+
+use crate::error::{Error, Result};
+use crate::indicators::tsf::Tsf;
+use crate::traits::Indicator;
+
+/// Time Series Forecast Oscillator — the percentage gap between the close and
+/// the **one-bar-ahead** time-series forecast of the close.
+///
+/// ```text
+/// TSFOsc_t = 100 · (close_t − TSF(close, period)_t) / close_t
+/// ```
+///
+/// where [`Tsf`](crate::Tsf) projects the rolling least-squares line one bar
+/// past the window (`a + b·period`). It is the close-relative companion to
+/// [`Cfo`](crate::Cfo), which measures the same percentage gap against the
+/// regression value at the *current* bar (`a + b·(period − 1)`). Because `TSF`
+/// advances one bar further than `LinearRegression`, the two differ by exactly
+/// the slope term `100·b/close`: on a trending series `TSFOsc` reads more
+/// negative in an uptrend (the forecast has already stepped above price) and
+/// more positive in a downtrend.
+///
+/// Positive readings mean the close sits *above* its forward forecast (price
+/// has overshot the projected trend); negative readings mean it sits below.
+/// Wraps the existing `Tsf` so the warmup matches.
+///
+/// # Example
+///
+/// ```
+/// use wickra_core::{Indicator, TsfOscillator};
+///
+/// let mut indicator = TsfOscillator::new(14).unwrap();
+/// let mut last = None;
+/// for i in 0..40 {
+///     last = indicator.update(100.0 + f64::from(i));
+/// }
+/// assert!(last.is_some());
+/// ```
+#[derive(Debug, Clone)]
+pub struct TsfOscillator {
+    period: usize,
+    tsf: Tsf,
+    current: Option<f64>,
+}
+
+impl TsfOscillator {
+    /// Construct a new TSF oscillator over `period` inputs.
+    ///
+    /// # Errors
+    /// Returns [`Error::InvalidPeriod`] if `period < 2` — a regression line is
+    /// undefined for fewer than two points.
+    pub fn new(period: usize) -> Result<Self> {
+        if period < 2 {
+            return Err(Error::InvalidPeriod {
+                message: "TSF oscillator needs period >= 2",
+            });
+        }
+        Ok(Self {
+            period,
+            tsf: Tsf::new(period)?,
+            current: None,
+        })
+    }
+
+    /// Configured period.
+    pub const fn period(&self) -> usize {
+        self.period
+    }
+}
+
+impl Indicator for TsfOscillator {
+    type Input = f64;
+    type Output = f64;
+
+    fn update(&mut self, input: f64) -> Option<f64> {
+        let forecast = self.tsf.update(input)?;
+        // Hold the previous value if the close is zero — the percentage form
+        // is undefined and a return of inf would propagate badly.
+        if input == 0.0 {
+            return self.current;
+        }
+        let value = 100.0 * (input - forecast) / input;
+        self.current = Some(value);
+        Some(value)
+    }
+
+    fn reset(&mut self) {
+        self.tsf.reset();
+        self.current = None;
+    }
+
+    fn warmup_period(&self) -> usize {
+        self.period
+    }
+
+    fn is_ready(&self) -> bool {
+        self.current.is_some()
+    }
+
+    fn name(&self) -> &'static str {
+        "TsfOscillator"
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::traits::BatchExt;
+    use approx::assert_relative_eq;
+
+    #[test]
+    fn rejects_short_period() {
+        assert!(matches!(
+            TsfOscillator::new(1),
+            Err(Error::InvalidPeriod { .. })
+        ));
+        assert!(matches!(
+            TsfOscillator::new(0),
+            Err(Error::InvalidPeriod { .. })
+        ));
+    }
+
+    #[test]
+    fn accessors_and_metadata() {
+        let osc = TsfOscillator::new(14).unwrap();
+        assert_eq!(osc.period(), 14);
+        assert_eq!(osc.warmup_period(), 14);
+        assert_eq!(osc.name(), "TsfOscillator");
+        assert!(!osc.is_ready());
+    }
+
+    #[test]
+    fn reference_value() {
+        // period 3 over [1, 2, 9]: fit y = 0 + 4x, one-bar-ahead TSF at x = 3
+        // is 12. With close = 9, TSFOsc = 100·(9 − 12)/9 = −33.3333…%.
+        let mut osc = TsfOscillator::new(3).unwrap();
+        let out = osc.batch(&[1.0_f64, 2.0, 9.0]);
+        assert!(out[0].is_none());
+        assert!(out[1].is_none());
+        assert_relative_eq!(out[2].unwrap(), -100.0 / 3.0, epsilon = 1e-9);
+        assert!(osc.is_ready());
+    }
+
+    #[test]
+    fn constant_series_yields_zero() {
+        // On a flat series the regression slope is 0, so the one-bar-ahead TSF
+        // equals the constant and close − forecast is exactly 0.
+        let mut osc = TsfOscillator::new(5).unwrap();
+        let out = osc.batch(&[42.0_f64; 30]);
+        for v in out.iter().skip(4).flatten() {
+            assert_relative_eq!(*v, 0.0, epsilon = 1e-12);
+        }
+    }
+
+    #[test]
+    fn linear_uptrend_reads_negative() {
+        // Unlike CFO (evaluated at the current bar), the forecast steps one bar
+        // ahead, so on a rising line the projection sits above the close and the
+        // oscillator is negative: TSFOsc = −100·slope/close.
+        let mut osc = TsfOscillator::new(5).unwrap();
+        let prices: Vec<f64> = (1..=20).map(|i| f64::from(i) * 2.0).collect();
+        let out = osc.batch(&prices);
+        for v in out.iter().skip(4).flatten() {
+            assert!(*v < 0.0, "uptrend forecast overshoots close, got {v}");
+        }
+    }
+
+    #[test]
+    fn warmup_emits_first_value_at_period() {
+        let mut osc = TsfOscillator::new(3).unwrap();
+        assert_eq!(osc.update(1.0), None);
+        assert_eq!(osc.update(2.0), None);
+        assert!(osc.update(3.0).is_some());
+    }
+
+    #[test]
+    fn batch_equals_streaming() {
+        let prices: Vec<f64> = (1..=80)
+            .map(|i| 100.0 + (f64::from(i) * 0.3).sin() * 5.0)
+            .collect();
+        let mut a = TsfOscillator::new(14).unwrap();
+        let mut b = TsfOscillator::new(14).unwrap();
+        assert_eq!(
+            a.batch(&prices),
+            prices.iter().map(|p| b.update(*p)).collect::<Vec<_>>()
+        );
+    }
+
+    #[test]
+    fn reset_clears_state() {
+        let mut osc = TsfOscillator::new(5).unwrap();
+        osc.batch(&(1..=20).map(f64::from).collect::<Vec<_>>());
+        assert!(osc.is_ready());
+        osc.reset();
+        assert!(!osc.is_ready());
+        assert_eq!(osc.update(1.0), None);
+    }
+
+    #[test]
+    fn zero_close_holds_value() {
+        let mut osc = TsfOscillator::new(3).unwrap();
+        osc.batch(&[1.0_f64, 2.0, 3.0]);
+        let before = osc.current;
+        assert_eq!(osc.update(0.0), before);
+    }
+}